Interpretive Summary: Yield attributes in U.S. Western Shipping type melon has not been rigorously studied since 1975. Since 1975 agricultural techniques of cultivation have changed to improve melon quality and yield. Because of these changes new commercial varieties have become more genetically similar. It is important to keep the genetic base (the genetic makeup) of commercial varieties as broad as possible since new pests can compromise the yield and quality of melon fruit production. New pests can reduce yield and quality by infecting melon plants. If commercial melon plants are similar then the pest can affect varieties to reduce yield and quality. One way to increase the genetic diversity (the genetic make-up of plants) is to introduce genes from wild exotic plants into commercial varieties. A wild plant type was discovered in Costa Rica that has potential to increase yield in U.S. Western Shipping type melon. Therefore, breeding strategies were implemented to incorporate economically important attributes (genes) from this exotic into commercial varieties. This breeding resulted in the creation of parental material that has potential for increasing yield in melon, but has not been adequately tested. Therefore, lines derived from this exotic were evaluated to determine their potential for advanced breeding and incorporation into commercial varieties. It was determined that the lines that have been developed have high yield potential and that these lines should be used in continued breeding. Hybrids derived from these lines have the potential to increase the genetic diversity of commercial melon. Increased genetic diversity would reduce the risk of pests uniformly destroying production fields. Thus, such plant material will increase sustained production and allow the grower opportunities to compete more effectively in the global market place. This will help to insure sustained growth in agricultural melon production.

Technical Abstract:
Plant architecture can be manipulated to increase yield in melon (Cucumis melo L.). A cross between a unique highly branched line, U. S. Department of Agriculture (USDA) 846-1 (P1; 7 to 11 lateral branches), and ‘Topmark’ (P2; 2 to 4 lateral branches), a U.S. Western Market type melon, produced F1 hybrid progeny and an array of 119 F3 families segregating for architectural habit and fruiting characteristics (hereafter designated yield components). A genetic analysis was conducted to estimate variances, heritabilities, and the number of effective factors for yield components by replicated evaluation of P1, P2, and their cross progeny (F1 and F3 families) at Arlington (AR) and Hancock (HCK), Wisconsin in 2001. Days to anthesis (DA), percentage of plants with early pistillate flowering (PPF), primary branch number (PB), fruit number per plant (FN), fruit weight per plant (FW), average weight per fruit (AWF), percentage of plants with predominantly crown fruit set (PCF), and percentage of plants with early maturing fruit (PMF) were evaluated. PB and FN exhibited mainly additive genetic variance, while FW and AWF demonstrated largely dominance genetic variance. Broad-sense heritabilities were 0.63 (AR) for DA, 0.64 (AR) for PPF, 0.85 (AR) and 0.83 (HCK) for AWF, 0.60 (AR) and 0.66 (HCK) for PCF, and 0.62 (AR) and 0.72 (HCK) for PMF. Narrow-sense heritabilities were 0.91 (AR) and 0.86 (HCK) for PB, 0.72 (AR) and 0.51 (HCK) for FN, and 0.45 (AR) and 0.28 (HCK) for FW. Estimations of the least number of effective factors for PB were relatively consistent at both AR (~ 4) and HCK (~ 2). Results suggest that remodeling plant architecture in U.S. Western Shipping type melons through the introgression of genes resident in highly branched melon types may lead to the development of high yielding melon cultivars with early, basally concentrated fruit suitable for once-over or machine harvesting operations.